Biochemical properties of a Flavobacterium johnsoniae dextranase and its biotechnological potential for Streptococcus mutans biofilm degradation.

Cariogenic biofilms have a matrix rich in exopolysaccharides (EPS), mutans and dextrans, that contribute to caries development. Although several physical and chemical treatments can be employed to remove oral biofilms, those are only partly efficient and use of biofilm-degrading enzymes represents an exciting opportunity to improve the performance of oral hygiene products. In the present study, a member of a glycosyl hydrolase family 66 from Flavobacterium johnsoniae (FjGH66) was heterologously expressed and biochemically characterized. The recombinant FjGH66 showed a hydrolytic activity against an early EPS-containing S. mutans biofilm, and, when associated with a α-(1,3)-glucosyl hydrolase (mutanase) from GH87 family, displayed outstanding performance, removing more than 80% of the plate-adhered biofilm. The mixture containing FjGH66 and Prevotella melaninogenica GH87 α-1,3-mutanase was added to a commercial mouthwash liquid to synergistically remove the biofilm. Dental floss and polyethylene disks coated with biofilm-degrading enzymes also degraded plate-adhered biofilm with a high efficiency. The results presented in this study might be valuable for future development of novel oral hygiene products.

The Screening and Identification of a Dextranase-Secreting Marine Actinmycete Saccharomonospora sp. K1 and Study of Its Enzymatic Characteristics.

In this study, an actinomycete was isolated from sea mud. The strain K1 was identified as Saccharomonospora sp. by 16S rDNA. The optimal enzyme production temperature, initial pH, time, and concentration of the inducer of this actinomycete strain K1 were 37 °C, pH 8.5, 72 h, and 2% dextran T20 of medium, respectively. Dextranase from strain K1 exhibited maximum activity at 8.5 pH and 50 °C. The molecular weight of the enzyme was <10 kDa. The metal ions Sr2+ and K+ enhanced its activity, whereas Fe3+ and Co2+ had an opposite effect. In addition, high-performance liquid chromatography showed that dextran was mainly hydrolyzed to isomaltoheptose and isomaltopentaose. Also, it could effectively remove biofilms of Streptococcus mutans. Furthermore, it could be used to prepare porous sweet potato starch. This is the first time a dextranase-producing actinomycete strain was screened from marine samples.

Preparation of Sweet Potato Porous Starch by Marine Dextranase and Its Adsorption Characteristics.

Dextranase (EC 3.2.1.11) is primarily applied in food, sugar, and pharmaceutical industries. This study focuses on using a cold shock Escherichia coli expression system to express marine dextranase SP5-Badex; enzyme activity increased about 2.2-fold compared to previous expression. This enzyme was employed to produce sweet potato porous starch, with special emphasis on the pore size of the starch. The water and oil adsorption rates of the porous starch increased by 1.43 and 1.51 times, respectively. Extensive Fourier transform infrared spectroscopy and X-ray diffraction revealed that the crystal structure of the sweet potato starch was unaltered by enzymatic hydrolysis. The adsorption capacities of the porous starch for curcumin and proanthocyanidins were 9.59 and 12.29 mg/g, respectively. Notably, the stability of proanthocyanidins was significantly enhanced through their encapsulation in porous starch. After 2.5 h of ultraviolet irradiation, the free radical scavenging rate of the encapsulated proanthocyanidins remained at 95.10%. Additionally, after 30 days of sunlight exposure, the free radical scavenging rate of the encapsulated proanthocyanidins (84.42%) was significantly higher than that (24.34%) observed in the control group. These research findings provide substantial experimental evidence for preparing sweet potato porous starch using marine dextranase.

Leuconostoc mesenteroides and Liquorilactobacillus mali strains, isolated from Algerian food products, are producers of the postbiotic compounds dextran, oligosaccharides and mannitol.

Six lactic acid bacteria (LAB) isolated from Algerian sheep's milk, traditional butter, date palm sap and barley, which produce dextran, mannitol, oligosaccharides and vitamin B2 have been characterized. They were identified as Leuconostoc mesenteroides (A4X, Z36P, B12 and O9) and Liquorilactobacillus mali (BR201 and FR123). Their exopolysaccharides synthesized from sucrose by dextransucrase (Dsr) were characterized as dextrans with (1,6)-D-glucopyranose units in the main backbone and branched at positions O-4, O-2 and/or O-3, with D-glucopyranose units in the side chain. A4X was the best dextran producer (4.5 g/L), while the other strains synthesized 2.1-2.7 g/L. Zymograms revealed that L. mali strains have a single Dsr with a molecular weight (Mw) of ~ 145 kDa, while the Lc. mesenteroides possess one or two enzymes with 170-211 kDa Mw. As far as we know, this is the first detection of L. mali Dsr. Analysis of metabolic fluxes from sucrose revealed that the six LAB produced mannitol (~ 12 g/L). The co-addition of maltose-sucrose resulted in the production of panose (up to 37.53 mM), an oligosaccharide known for its prebiotic effect. A4X, Z36P and B12 showed dextranase hydrolytic enzymatic activity and were able to produce another trisaccharide, maltotriose, which is the first instance of a dextranase activity encoded by Lc. mesenteroides strains. Furthermore, B12 and O9 grew in the absence of riboflavin (vitamin B2) and synthesized this vitamin, in a defined medium at the level of ~ 220 µg/L. Therefore, these LAB, especially Lc. mesenteroides B12, are good candidates for the development of new fermented food biofortified with functional compounds.

Modification of the Loop Region Near the Substrate Tunnel to Alter the Hydrolytic Process of Dextranase.

Dextranases are hydrolases that exclusively catalyze the disruption of α-1,6 glycosidic bonds. A series of variant enzymes were obtained by comparing the sequences of dextranases from different sources and introducing sequence substitutions. A correlation was found between the number of amino acids in the 397-401 region and the hydrolytic process. When there were no more than 5 amino acids in the 397-401 region, the enzyme first hydrolyzed the dextran T70 to a low molecular weight dextran with a molecular weight of about 5000, then IMOs1 appeared in the system if the degradation continued, showing a clear sequential relationship. And when there are more than 5 amino acids in the 397-401 region, IMOs were produced at the beginning of hydrolysis and continue to increase throughout the hydrolytic process. At the same time, we investigated the enzymatic properties of the variants and found that the hydrolytic rate of A-Ca was 11 times higher than that of the original enzyme. The proportion of IMOs produced by A-Ca was 80.68%, which was nearly10% higher than the original enzyme, providing a new enzyme for the industrial preparation of IMOs.

Dextranase Production Using Marine Microbacterium sp. XD05 and Its Application.

Dextranase, also known as glucanase, is a hydrolase enzyme that cleaves α-1,6 glycosidic bonds. In this study, a dextranase-producing strain was isolated from water samples of the Qingdao Sea and identified as Microbacterium sp. This strain was further evaluated for growth conditions, enzyme-producing conditions, enzymatic properties, and hydrolysates. Yeast extract and sodium chloride were found to be the most suitable carbon and nitrogen sources for strain growth, while sucrose and ammonium sodium were found to be suitable carbon and nitrogen sources for fermentation. The optimal pH was 7.5, with a culture temperature of 40 °C and a culture time of 48 h. Dextranase produced by strain XD05 showed good thermal stability at 40 °C by retaining more than 70% relative enzyme activity. The pH stability of the enzyme was better under a weak alkaline condition (pH 6.0-8.0). The addition of NH4+ increased dextranase activity, while Co2+ and Mn2+ had slight inhibitory effects on dextranase activity. In addition, high-performance liquid chromatography showed that dextran is mainly hydrolyzed to maltoheptanose, maltohexanose, maltopentose, and maltootriose. Moreover, it can form corn porous starch. Dextranase can be used in various fields, such as food, medicine, chemical industry, cosmetics, and agriculture.

Molecular docking and dynamics of a dextranase derived from Penicillium cyclopium CICC-4022.

This study aimed to investigate the recognition mechanism of dextranase (PC-Edex) produced by Penicillium cyclopium CICC-4022 on dextran. Whole genome information of P. cyclopium CICC-4022 was obtained through genome sequencing technology. The coding information of PC-Edex was determined based on the annotation of the protein-coding genes using protein databases. The three-dimensional structure of PC-Edex was obtained via homology modelling. The active site and binding free energy between PC-Edex and dextran were calculated by molecular docking and molecular dynamics techniques. The results showed that the total sequence length and GC content of P. cyclopium CICC-4022 were 29,710,801 bp and 47.02 %, respectively. The annotation of protein-encoding genes showed that P. cyclopium CICC-4022 is highly active and has many carbohydrate transport and metabolic functions, and most of its proteases are glycolytic anhydrases. Furthermore, the gene encoding PC-Edex was successfully annotated. Molecular dynamics simulations indicated that van der Waals interaction was the main driving force of interaction. Residues Ile114, Asp115, Tyr332, Lys344, and Gln403 significantly promoted the binding between dextran and PC-Edex. In summary, this study explored the active site catalyzed by PC-Edex based on the binding pattern of PC-Edex and dextran. Therefore, this study provides genomic information on dextranase and data supporting the rational modification and enhancement of PC-Edex.

Review on recent advances in the properties, production and applications of microbial dextranases.

Dextranase is a type of hydrolase that is responsible for catalyzing the breakdown of high-molecular-weight dextran into low-molecular-weight polysaccharides. This process is called dextranolysis. A select group of bacteria and fungi, including yeasts and likely certain complex eukaryotes, produce dextranase enzymes as extracellular enzymes that are released into the environment. These enzymes join dextran's α-1,6 glycosidic bonds to make glucose, exodextranases, or isomalto-oligosaccharides (endodextranases). Dextranase is an enzyme that has a wide variety of applications, some of which include the sugar business, the production of human plasma replacements, the treatment of dental plaque and its protection, and the creation of human plasma replacements. Because of this, the quantity of studies carried out on worldwide has steadily increased over the course of the past couple of decades. The major focus of this study is on the most current advancements in the production, administration, and properties of microbial dextranases. This will be done throughout the entirety of the review.

Dextranase enzyme and Enterococcus faecium probiotic have anti-biofilm effects by reducing the count of bacteria in dental plaque in the oral cavity of dogs.

OBJECTIVE: Periodontal disease is a common clinical complication and has a negative impact on the quality of life and the welfare of companion dogs. Periodontal disease occurs when pathogenic bacteria are accumulated in the gingival sulcus, which favors biofilm formation. The oral health of dogs can be significantly compromised by dental plaque accumulation. Thus, this investigation demonstrates the effect of Enterococcus faecium probiotic, dextranase enzyme, and their combination on dental biofilm in the oral cavity of dogs. ANIMALS: The 30 dogs were referred to Polyclinic with no oral ulcers, severe periodontitis, and internal diseases. PROCEDURES: Dextranase enzyme, E faecium probiotic, and their combination were administered in the oral cavity of dogs. Microbiological samples were obtained from tooth surfaces and gums before and after intervention with the substances. Bacterial colonies were enumerated by using a colony counter. Also, Porphyromonas gingivalis hmuY gene expression was evaluated by reverse transcription quantitative real-time PCR analysis. RESULTS: The total colony count of the bacterial culture indicated that the dextranase enzyme, E faecium probiotic, and their combination significantly reduced the total bacteria count in the oral cavity. Moreover, in the reverse transcription quantitative real-time PCR analysis it was observed that using the combination of E faecium probiotic and dextranase enzyme decreases the hmuY gene expression of P gingivalis bacteria. CLINICAL RELEVANCE: The results clearly indicated that the dextranase enzyme and E faecium probiotic could be used as preventive agents to reduce oral biofilm in dogs. Furthermore, no side effects were observed while using these substances.

Immobilization of Dextranase Obtained from the Marine Cellulosimicrobium sp. Y1 on Nanoparticles: Nano-TiO2 Improving Hydrolysate Properties and Enhancing Reuse.

Dextranase is widely used in sugar production, drug synthesis, material preparation, and biotechnology, among other fields. The immobilization of dextranase using nanomaterials in order to make it reusable, is a hot research topic. In this study, the immobilization of purified dextranase was performed using different nanomaterials. The best results were obtained when dextranase was immobilized on titanium dioxide (TiO2), and a particle size of 30 nm was achieved. The optimum immobilization conditions were pH 7.0, temperature 25 °C, time 1 h, and immobilization agent TiO2. The immobilized materials were characterized using Fourier-transform infrared spectroscopy, X-ray diffractometry, and field emission gun scanning electron microscopy. The optimum temperature and pH of the immobilized dextranase were 30 °C and 7.5, respectively. The activity of the immobilized dextranase was >50% even after 7 times of reuse, and 58% of the enzyme was active even after 7 days of storage at 25 °C, indicating the reproducibility of the immobilized enzyme. The adsorption of dextranase by TiO2 nanoparticles exhibited secondary reaction kinetics. Compared with free dextranase, the hydrolysates of the immobilized dextranase were significantly different, and consisted mainly of isomaltotriose and isomaltotetraose. The highly polymerized isomaltotetraose levels could reach >78.69% of the product after 30 min of enzymatic digestion.

Reliable N-Glycan Analysis-Removal of Frequently Occurring Oligosaccharide Impurities by Enzymatic Degradation.

Glycosylation, especially N-glycosylation, is one of the most common protein modifications, with immense importance at the molecular, cellular, and organismal level. Thus, accurate and reliable N-glycan analysis is essential in many areas of pharmaceutical and food industry, medicine, and science. However, due to the complexity of the cellular glycosylation process, in-depth glycoanalysis is still a highly challenging endeavor. Contamination of samples with oligosaccharide impurities (OSIs), typically linear glucose homo-oligomers, can cause further complications. Due to their physicochemical similarity to N-glycans, OSIs produce potentially overlapping signals, which can remain unnoticed. If recognized, suspected OSI signals are usually excluded in data evaluation. However, in both cases, interpretation of results can be impaired. Alternatively, sample preparation can be repeated to include an OSI removal step from samples. However, this significantly increases sample amount, time, and effort necessary. To overcome these issues, we investigated the option to enzymatically degrade and thereby remove interfering OSIs as a final sample preparation step. Therefore, we screened ten commercially available enzymes concerning their potential to efficiently degrade maltodextrins and dextrans as most frequently found OSIs. Of these enzymes, only dextranase from Chaetomium erraticum and glucoamylase P from Hormoconis resinae enabled a degradation of OSIs within only 30 min that is free of side reactions with N-glycans. Finally, we applied the straightforward enzymatic degradation of OSIs to N-glycan samples derived from different standard glycoproteins and various stem cell lysates.

Molecular Docking and Site-Directed Mutagenesis of GH49 Family Dextranase for the Preparation of High-Degree Polymerization Isomaltooligosaccharide.

The high-degree polymerization of isomaltooligosaccharide (IMO) not only effectively promotes the growth and reproduction of Bifidobacterium in the human body but also renders it resistant to rapid degradation by gastric acid and can stimulate insulin secretion. In this study, we chose the engineered strain expressed dextranase (PsDex1711) as the research model and used the AutoDock vina molecular docking technique to dock IMO4, IMO5, and IMO6 with it to obtain mutation sites, and then studied the potential effect of key amino acids in this enzyme on its hydrolysate composition and enzymatic properties by site-directed mutagenesis method. It was found that the yield of IMO4 increased significantly to 62.32% by the mutant enzyme H373A. Saturation mutation depicted that the yield of IMO4 increased to 69.81% by the mutant enzyme H373R, and its neighboring site S374R IMO4 yield was augmented to 64.31%. Analysis of the enzymatic properties of the mutant enzyme revealed that the optimum temperature of H373R decreased from 30 °C to 20 °C, and more than 70% of the enzyme activity was maintained under alkaline conditions. The double-site saturation mutation results showed that the mutant enzyme H373R/N445Y IMO4 yield increased to 68.57%. The results suggest that the 373 sites with basic non-polar amino acids, such as arginine and histidine, affect the catalytic properties of the enzyme. The findings provide an important theoretical basis for the future marketable production of IMO4 and analysis of the structure of dextranase.

Improving the thermostability of GH49 dextranase AoDex by site-directed mutagenesis.

As an indispensable enzyme for the hydrolysis of dextran, dextranase has been widely used in the fields of food and medicine. It should be noted that the weak thermostability of dextranase has become a restricted factor for industrial applications. This study aims to improve the thermostability of dextranase AoDex in glycoside hydrolase (GH) family 49 that derived from Arthrobacter oxydans KQ11. Some mutants were predicted and constructed based on B-factor analysis, PoPMuSiC and HotMuSiC algorithms, and four mutants exhibited higher heat resistance. Compared with the wild-type, mutant S357P showed the best improved thermostability with a 5.4-fold increase of half-life at 60 °C, and a 2.1-fold increase of half-life at 65 °C. Furthermore, S357V displayed the most obvious increase in enzymatic activity and thermostability simultaneously. Structural modeling analysis indicated that the improved thermostability of mutants might be attributed to the introduction of proline and hydrophobic effects, which generated the rigid optimization of the structural conformation. These results illustrated that it was effective to improve the thermostability of dextranase AoDex by rational design and site-directed mutagenesis. The thermostable mutant of dextranase AoDex has potential application value, and it can also provide references for engineering other thermostable dextranases of the GH49 family.

Purification and characterization of cold-adapted and salt-tolerant dextranase from Cellulosimicrobium sp. THN1 and its potential application for treatment of dental plaque.

The cold-adapted and/or salt-tolerant enzymes from marine microorganisms were confirmed to be meritorious tools to enhance the efficiency of biocatalysis in industrial biotechnology. We purified and characterized a dextranase CeDex from the marine bacterium Cellulosimicrobium sp. THN1. CeDex acted in alkaline pHs (7.5-8.5) and a broad temperature range (10-50°C) with sufficient pH stability and thermostability. Remarkably, CeDex retained approximately 40% of its maximal activities at 4°C and increased its activity to 150% in 4 M NaCl, displaying prominently cold adaptation and salt tolerance. Moreover, CeDex was greatly stimulated by Mg2+, Na+, Ba2+, Ca2+ and Sr2+, and sugarcane juice always contains K+, Ca2+, Mg2+ and Na+, so CeDex will be suitable for removing dextran in the sugar industry. The main hydrolysate of CeDex was isomaltotriose, accompanied by isomaltotetraose, long-chain IOMs, and a small amount of isomaltose. The amino acid sequence of CeDex was identified from the THN1 genomic sequence by Nano LC-MS/MS and classified into the GH49 family. Notably, CeDex could prevent the formation of Streptococcus mutans biofilm and disassemble existing biofilms at 10 U/ml concentration and would have great potential to defeat biofilm-related dental caries.

Development of thermostable dextranase from Streptococcus mutans (SmdexTM) through in silico design employing B-factor and Cartesian-ΔΔG.

The thermal stability of enzymes dramatically limits their application in the industrial field. Based on the crystal structure, we conducted a semi-rational design according to the B-factor and free energy values to improve the stability of dextranase from Streptococcus mutans (SmdexTM). The B-factor values of Asn102, Asn503, Asp501 and Asp500 were the highest predicted by B-FITTER. Then Rosetta was used to simulate the saturation mutations of Asn102, Asn503, Asp501 and Asp500. The mutated amino acid was designed according to the change of acG. The results showed that the thermal stability of N102P, N102C, D500G, and D500T was improved, and the half-lives of N102P/D500G and N102P/D500T at 45 °C were increased to 3.14 times and 2.44 times, respectively. Analyzing the interaction of amino acids by using Discovery Studio 4.5, it was observed that the thermal stability of dextranase was improved due to the increase in hydrophobicity and the number of hydrogen bonds of the mutant enzyme. The catalytic efficiency of N102P/D500T was increased. Compared with the hydrolyzed products of SmdexTM, the mutant enzymes do not change the specificity of hydrolysates.

Marine Bacterial Dextranases: Fundamentals and Applications.

Dextran, a renewable hydrophilic polysaccharide, is nontoxic, highly stable but intrinsically biodegradable. The α-1, 6 glycosidic bonds in dextran are attacked by dextranase (E.C. 3.2.1.11) which is an inducible enzyme. Dextranase finds many applications such as, in sugar industry, in the production of human plasma substitutes, and for the treatment and prevention of dental plaque. Currently, dextranases are obtained from terrestrial fungi which have longer duration for production but not very tolerant to environmental conditions and have safety concerns. Marine bacteria have been proposed as an alternative source of these enzymes and can provide prospects to overcome these issues. Indeed, marine bacterial dextranases are reportedly more effective and suitable for dental caries prevention and treatment. Here, we focused on properties of dextran, properties of dextran-hydrolyzing enzymes, particularly from marine sources and the biochemical features of these enzymes. Lastly the potential use of these marine bacterial dextranase to remove dental plaque has been discussed. The review covers dextranase-producing bacteria isolated from shrimp, fish, algae, sea slit, and sea water, as well as from macro- and micro fungi and other microorganisms. It is common knowledge that dextranase is used in the sugar industry; produced as a result of hydrolysis by dextranase and have prebiotic properties which influence the consistency and texture of food products. In medicine, dextranases are used to make blood substitutes. In addition, dextranase is used to produce low molecular weight dextran and cytotoxic dextran. Furthermore, dextranase is used to enhance antibiotic activity in endocarditis. It has been established that dextranase from marine bacteria is the most preferable for removing plaque, as it has a high enzymatic activity. This study lays the groundwork for the future design and development of different oral care products, based on enzymes derived from marine bacteria.

Study of key amino acid residues of GH66 dextranase for producing high-degree polymerized isomaltooligosaccharides and improving of thermostability.

Obtaining high-degree polymerized isomaltose is more difficult while achieving better prebiotic effects. We investigated the mutation specificity and enzymatic properties of SP5-Badex, a dextranase from the GH66 family of Bacillus aquimaris SP5, and determined its mutation sites through molecular docking to obtain five mutants, namely E454K, E454G, Y539F, N369F, and Y153N. Among them, Y539F and Y153N exhibited no enzymatic activity, but their hydrolysates included isomaltotetraose (IMO4). The enzymatic activity of E454G was 1.96 U/ml, which was 3.08 times higher than that before mutation. Moreover, 70% of the enzymatic activity could be retained after holding at 45°C for 180 min, which was 40% higher than that of SP5-Badex. Furthermore, its IMO4 content was 5.62% higher than that of SP5-Badex after hydrolysis at 30°C for 180 min. To investigate the effect of different amino acids on the same mutation site, saturation mutation was induced at site Y153, and the results showed that the enzyme activity of Y153W could be increased by 2 times, and some of the enzyme activity could still be retained at 50°C. Moreover, the enzyme activity increased by 50% compared with that of SP5-Badex after holding at 45°C for 180 min, and the IMO4 content of Y153W was approximately 64.97% after hydrolysis at 30°C for 180 min, which increased by approximately 12.47% compared with that of SP5-Badex. This site is hypothesized to rigidly bind to nonpolar (hydrophobic) amino acids to improve the stability of the protein structure, which in turn improves the thermal stability and simultaneously increases the IMO4 yield.

Safety evaluation of the food enzyme dextranase from the Collariella gracilis strain AE-DX.

The food enzyme dextranase (6-α-d-glucan 6-glucanohydrolase, EC 3.2.1.11) is produced with the non-genetically modified Collariella gracilis strain AE-DX by Amano Enzyme Inc. The food enzyme is considered free from viable cells of the production organism. The food enzyme is intended to be used in refined sugar production from sugar beet or sugar cane. Since residual amounts of total organic solids (TOS) are removed by crystallisation during the production of refined white sucrose, dietary exposure was not considered necessary for refined sugars. However, beet molasses and cane syrups, by-products from sugar production, could enter the food chain. Based on the maximum use levels recommended, dietary exposure was estimated to be up to 0.39 mg TOS/kg body weight (bw) per day via the consumption of unrefined sugars. Genotoxicity tests did not indicate a safety concern. The systemic toxicity was assessed by means of a repeated dose 90-day oral toxicity study in rats. The Panel identified a lowest observed adverse effect level (LOAEL) of 940.5 mg TOS/kg bw per day, the lowest dose tested, which when compared with the estimated dietary exposure, results in a margin of exposure of more than 800. A search for similarity of the amino acid sequence of the food enzyme to known allergens was made and no matches were found. The Panel considered that, under the intended conditions of use, the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood for this to occur is considered to be low. Based on the data provided, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

Pickering emulsions stabilized by biodegradable dextran-based nanoparticles featuring enzyme responsiveness and co-encapsulation of actives.

In this study, Pickering emulsions of dodecane and medium chain triglyceride (MCT) oils were stabilized by simply alkylated-dextran nanoparticles. Our findings show that very little of these bio-friendly nanoparticles is necessary to stabilize Pickering emulsions while providing a high time stability (more than a year at 37 °C). As dextran is known to be cleavable by dextranase enzyme, hydrolysis of the nanoparticles in the presence of dextranase could be achieved. This allowed performing on-demand destabilization of Pickering emulsions. Furthermore, two different fluorescent probes were loaded into the stabilizing particles and the oil droplets respectively, providing a proof of concept for co-encapsulation of actives in advanced delivery applications. Additionally, to a conventional fluorescence probe, quinine, an antimalarial drug was also encapsulated into the nanoparticles.

Purification and characterization of dextranase from Penicillium cyclopium CICC-4022 and its degradation of dextran.

A dextranase was purified from Penicillium cyclopium CICC-4022 by ammonium sulfate fractionation and secondary tangential flow filtration, and the enzymatic properties were studied. The purified dextranase was used to regulated the molecular mass and homogeneity of dextran. Weight-average molecular mass (Mw) and polydispersity index (Mw/Mn) of dextran were measured by gel permeation chromatography (GPC) coupled with a triple-detector array (GPC-TDA), which is composed of a multiple-angle light scattering, a viscometer, and a refractive-index detector. The dextranase was purified by 2.24-fold, the recovery rate was 45.84%, the specific activity was 1442.05 U/mg, and the Mw was 77 KDa. Dextranase showed maximum activity at pH of 5.0 and 55 °C. Na+, K+ and NH4+ can effectively improve the dextranase activity, Cu2+ and Pb2+ can strongly inhibit the dextranase activity. Dextranase specifically degraded the α-1,6 glycosidic bonds of dextran. By controlling the dextranase activity, substrate concentration, and time, the specific Mw dextran with good homogeneity was obtained. The structure of dextran was not altered before or after dextranase hydrolysis, but its conformation changed from a spherical chain to a compliant chain. When the Mw of the dextran product was about 5 KDa, it was a compact spherical chain conformation in solution.